This invention relates to shaft mounted drive components, and more particularly, this invention relates to a shaft mounted cluster roller assembly used in material handling applications.
Cluster roller assemblies are used in container translating and orienting apparatus, such as disclosed in U.S. Pat. Nos. 4,981,209 and 5,064,045 assigned to FMC Corporation, the disclosures which are hereby incorporated by reference in their entirety. In these types of apparatus, the movement of flat bottomed articles is controlled in a plurality of different directions relative to a supporting platform. The article is supported on a plurality of clusters of helically arranged, freely rotatable rollers mounted on a plurality of shafts. The different shafts or groups of shafts lie in one of a plurality of zones and are selectively driven in a clockwise direction, a counter-clockwise direction, or held stationary. Selective control of various drive shafts enables the apparatus to move an article parallel to the longitudinal axis of the platform in two selected directions, perpendicular to the longitudinal axis in two selected directions, diagonally of the longitudinal axis in four selected directions, and either clockwise or counter-clockwise about an axis normal to the flat bottom of the article.
The 45xc2x0 angle of a roller relative to a body member and the use of the conveyor platform in adverse environments causes dirt, aluminum oxides and other contaminants to pass through the roller inside the various bushings, reducing the usable life of a roller by three or four times. One example of the type of bushing and washer used with a cluster roller assembly as described is disclosed in U.S. Pat. No. 5,064,045 assigned to FMC Corporation, the disclosure which is hereby incorporated by reference in its entirety.
In that patent, a cluster roller assembly for material handing conveyor has a plurality of rollers mounted on a body member at an acute angle to the axis defined by the drive shaft. A bushing is pressed into and recessed from each end of the roller to provide a consistent, frictional force between the roller and the body member under various conditions of moisture. The roller is mounted for rotation on a shaft and extends between a pair of outwardly, extending support legs formed on the body member along the periphery. The shaft is retained in this position and restrained from rotation by a flat formed on one end of the shaft which end terminates in a reduced diameter threaded portion for receiving a nut.
Flat washers are positioned on the roller shaft between the ends of the roller and the inner side of the support legs. These washers are made of a hard material having a low coefficient of friction with the body member, e.g., an aluminum alloy. The washers in that disclosure could be molybdenum filled nylon. The bushings are a material compatible with the roller shaft, typically made from stainless steel, and possesses a low coefficient of friction. One type of bushing used in those applications is a mild steel coated with a porous bronze, which has been impregnated with polytetrafluoroethylene and lead.
This combination of flat nylon washers at the ends of the roller and bushings engage the steel shaft. However, accuracy is not always provided in wet conditions. The oil that provides lubrication could be washed out while contaminants are washed into the rollers. The rolling friction could increase to a point where any ULD control is lost because of side shift and rotation functions. Although the washer and composite bushings at each end of the rollers can reduce rolling friction, the contaminants enter the roller between the bushing and pin, or roller shaft, on which the roller rotates, as well as thrust washer areas, which shortens the useful life of the bushings and thrust washers. It is therefore essential to provide a roller that can operate efficiently in very wet climates and withstand to a greater degree the contaminants that pass into the rollers, and also provide for full operation as described above over extended years of service.
In accordance with the present invention, a cluster roller assembly for use in material handling includes a body member that mounts on a driven shaft. The body member includes a periphery having a plurality of roller support positions. A pair of support legs are mounted at each roller support position. A roller is supported by each pair of support legs, and each roller includes a central bore extending through either end of the roller to define an axis of rotation.
A bearing recess is formed at either end of the roller. A pair of rolling element bearings are each fitted within the bearing recess and each has an inner race. A roller shaft extends through the central bore. The rolling element bearings engage at either end a pair of support legs formed on the body member, which support the roller. In one aspect of the invention, it is possible to include a spacer that engages the rolling element bearing and engages the inner race of the rolling element bearing and passes the thrust load of the roller onto the spacer and the body member. It is also possible to use an extended inner race that engages the support area of the casting. It is also possible that the rolling element bearing is sealed.
In still another aspect of the present invention, if a spacer is used, the spacer includes a circumferentially extending mounting flange that frictionally engages the rolling element bearing to retain the annular spacer onto the rolling element bearing. It also can provide a seal. Rollers are disposed at an acute angle relative to the axis of rotation. Rollers also have an outer surface that is barrel shaped and configured to trace a helical pattern of contact with an article.
In still another aspect of the present invention, a conveyor permits translation or rotation of an article and includes a frame and a plurality of drive shafts rotatably mounted on the frame and positioned substantially parallel to each other. Each drive shaft includes a plurality of cluster roller assemblies mounted thereon. Each of the cluster roller assemblies comprises a body member having a periphery and plurality of roller support positions along the periphery. A pair of support legs are formed at each roller support position and a roller is supported by each pair of support legs. The roller is formed as before with a central bore, bearing recess, rolling element bearings, roller shaft and spacer.